An invisible man is here to see you
Nurse: Doctor, there is an invisible man in your waiting room.

Doctor: Tell him I can't see him now. Next.

4 Doctors
Four surgeons were taking a coffee break and were discussing their work.

The first said, "I think accountants are the easiest to operate on. You open them up and everything inside is numbered."

The second said, "I think librarians are the easiest to operate on. You open them up and everything inside is in alphabetical order."

The third said, "I like to operate on electricians. You open them up and everything inside is color-coded."

The fourth one said, "I like to operate on lawyers. They're heartless, spineless, gutless, and their heads and their asses are interchangeable."